Search

The efficacy of NS5A inhibitors against several less common subtypes of hepatitis C virus (HCV) is poorly characterised. Some subtypes including 3b, 3g, 6u and 6v commonly harbour amino acid residues in NS5A that may confer resistance to direct-acting antivirals (DAAs) in other common subtypes. Data from patients also suggest that 1l and 4r with amino acid substitutions at positions 28-31 and 93 in NS5A are relatively resistant to DAA therapy. In this study, we tested the efficacy of daclatasvir, elbasvir, ledipasvir, pibrentasvir and velpatasvir against these subtypes using the SGR-JFH1 replicon backbone. NS5A inhibitors showed different levels of efficacy with only pibrentasvir effective against all tested subtypes. Daclatasvir and ledipasvir were ineffective against 6u and 6v (half maximal effective concentration [EC 50 ] values of 239–321 nM) while 3b and 3g were only susceptible to pibrentasvir. Analysis of effects of individual mutations indicated that Q30R in 1l increased the EC 50 of ledipasvir by 18-fold, conferring intermediate resistance, while those of L31M and Y93H in 4r induced increases in EC 50 values of 2,100- and 3,575-fold (high-level resistance). The high ledipasvir EC 50 values of 1l with the Q30R substitution, 4r L31M and 4r Y93H may explain the treatment failure in patients who were infected with these viruses and treated with ledipasvir + sofosbuvir. This study also shows the ineffectiveness of the first generation NS5A inhibitors against 6u and 6v, and confirms the inherent resistance of 3b and 3g to most NS5A inhibitors. Clinical studies to confirm in vivo sensitivity to NS5A inhibitors are urgently needed so that rational, effective treatment strategies may be developed for unusual subtypes. Little is known about the efficacy of NS5A inhibitors against some "unusual" hepatitis C virus (HCV) subtypes including 1l, 3b, 3g, 4r, 6u and 6v. In this study, we manufactured HCV replicons which express the NS5A protein from the unusual HCV subtypes 1l, 3b, 3g, 4r, 6u, 6v. We then tested the effect of the NS5A inhibitors daclatasvir, elbasvir, ledipasvir, pibrentasvir and velpatasvir on blocking replication, using these replicons. We show that these replicons are resistant at some level to all NS5A inhibitors other than pibrentasvir. • The "unusual" HCV subtypes 1l, 3b, 3g, 4r, 6u and 6v show variable levels of resistance to all NS5A inhibitors in vitro. • Pibrentasvir shows the greatest level of activity against all the unusual subtypes. • HCV subtypes 3b and 3g are resistant to all NS5A inhibitors other than pibrentasvir in in vitro testing. • Daclatasvir and ledipasvir are ineffective against subtypes 6u and 6v in in vitro testing. • The presence of the resistance-associated substitutions Q30R in 1l, and L31M or Y93H in 4r confers resistance to ledipasvir. [ABSTRACT FROM AUTHOR]